The present invention relates to a wing arrangement for an aircraft comprising a wing having a base section and a tip section, the base section having a first end portion and a second end portion, the tip section having a third end portion and a fourth end portion, wherein the first end portion is adapted to be coupled to the fuselage of the aircraft and wherein the second end portion and the third end portion are coupled with each other so that the tip section is pivotable with respect to the base section about a pivot axis.
The aspect ratio, i.e. the ratio of span to chord, of an aircraft wing is one factor influencing the efficiency of the aircraft during flight. Generally, an increase of the aspect ratio is associated with an increased efficiency during steady flight. Therefore, an increase of the wingspan of an aircraft is one factor to take into consideration when seeking to reduce fuel consumption. However, when elongating the wing of an existing family of aircraft, it may become necessary to adapt the aircraft family specific infrastructure, and airport fees may increase.
One possibility to increase the wingspan without having to adapt the aircraft family specific infrastructure and having to deal with increased airport fees, or to reduce airport fees for existing aircraft is to provide for a foldable wing construction which allows to pivotably move an outboard end portion of the wing between a deployed position, in which the wing has its normal flight configuration, and a stowed position, in which the wing has a folded configuration and the wingspan is decreased as compared to the deployed position.
A wing arrangement is disclosed having a foldable wing which is safe and reliable in operation and has at the same time of a simple construction.
Hence, a wing arrangement is disclosed including a wing having a base section and a tip section, the base section having a first end portion and a second end portion, the tip section having a third end portion and a fourth end portion, wherein the first end portion is adapted to be coupled to the fuselage of the aircraft. The second end portion and the third end portion are coupled with each other by a coupling arrangement so that the tip section is pivotable with respect to the base section about a pivot axis. In particular, a pivotal movement of the tip section relative to the base section between a stowed position and a deployed position is enabled, wherein the spanwise length of the wing is larger in the deployed position than in the stowed position. In other words, the length of the entire wing measured parallel to the y-axis of the aircraft to which the wing arrangement is coupled, is larger in the deployed position than in the stowed position.
Thus, the wing arrangement is formed of two sections, namely the base section intended to be secured to the fuselage of the aircraft and the tip section pivotably connected to the distal end of the base section. Further, in a preferred embodiment the pivot axis may extend nearly parallel to the z-axis of the aircraft on which the wing arrangement of the present invention is mounted. In particular, it can be tilted by 15° with respect to the vertical direction or z-axis so that when the tip section pivots rearwards or forwards from the deployed position in which the tip section is aligned with the longitudinal axis of the base section, to the stowed position, the distal end of the tip section moves upwards.
The coupling arrangement comprises an annular outer part and an annular inner part, and one of the annular outer part and the annular inner part is fixedly coupled to the second end portion whereas the other of the annular outer part and the annular inner part is fixedly coupled to the third end portion. In particular, it is preferred that the annular outer part is fixedly coupled to the second end portion and the annular inner part is fixedly coupled the third end portion.
The annular outer part extends in a plane perpendicular to the pivot axis and at least partially surrounds a receiving space, wherein the annular inner part is at least partially received in the receiving space and the annular inner part at least partially surrounds an actuator space. Further, the annular outer part and the annular inner part are configured such that the annular inner part is guided by the annular outer part inside the receiving space for the pivot movement about the pivot axis between the deployed and stowed positions. Thus, the annular inner and outer parts form a bearing arrangement, which guides the pivotal movement of the tip section relative to the base section. Further, a free space is provided inside the annular inner part in the center of the bearing arrangement, and this free space extends along the pivot axis about which the tip section pivots.
The coupling arrangement further comprises an actuator received in this free space or actuator space, and the actuator comprises a base member and an output member which is pivotably mounted on the base member. The base member is fixedly coupled to the second end portion, and hence the base section, whereas the output member is fixedly coupled to the third end portion, i.e. the tip section. So, the output member may pivot with respect to the base member about the pivot axis, and the actuator comprises drive means coupled to the base member and the output member and being adapted such that when the drive means are actuated a pivotal movement of the output member relative to the base member about the pivot axis is effected.
Here, it has to be noted, that when two elements are described as being fixedly coupled, this includes both a direct connection without any intermediate elements and an indirect connection with intermediate elements between the elements being coupled. However, in any case the spatial relationship between those elements described as being fixedly coupled cannot change.
Thus, in the configuration of the present invention the actuator which effects the pivotal movement of the tip section relative to the base section is arranged in the center of the bearing arrangement for pivotably supporting the tip section on the base section of the wing. This allows to couple the base member and the driven output member of the actuator with the second end portion and the third end portion in a way in which the distance these connections have to the pivot axis, can be minimized. However, those sections of the second and the third end portions being in the load path between the annular inner and outer parts and the connection to the actuator are subject to loads during the pivotal movement and have to be designed such that these loads can be borne by the respective sections. Since in the configuration of the present invention these load paths can be kept short, only small parts of both the second and the third end portions have to be designed with a high structural stability which leads to weight savings.
A further advantage is that the actuator and the respective coupling assembly do not extend over a big area but are arranged in the vicinity of the bearing arrangement which facilitates maintenance of the actuator.
In a preferred embodiment, the annular outer part is formed as an outer ring member being circular or having the shape of a segment of a circle and having an inner support surface, and the annular inner part is formed as an inner ring member being circular or having the shape of a segment of a circle and having an outer support surface. The inner support surface at least partially abuts on the outer support surface. Such an arrangement results in small dimensions of the combination of the annular outer and inner parts in the direction of pivot axis which is particularly advantageous when the pivot axis extends nearly parallel to the z-axis of the respective aircraft.
In order to increase stability of the bearing arrangement formed by the ring members, one of the inner support surface and the outer support surface comprises at least one protrusion extending radially with respect to the pivot axis and the other of the inner support surface and the outer support surface comprises an annular recess extending radially with respect to the pivot axis. The at least one protrusion and the recess are configured such that the protrusion extends into the recess.
In a further preferred embodiment a first coupling member is provided which extends over the actuator space, wherein the coupling member is fixedly coupled to the third end portion and comprises a first engagement member being accessible from the actuator space. The output member comprises a second engagement member, being in engagement with the first engagement member, wherein the first and the second engagement members are configured such that when being in engagement with each other torque supplied by the output member is transferred to the coupling member and that the second engagement member can be disengaged from the first engagement member by a linear movement of the actuator along the pivot axis.
Firstly, such an arrangement allows to minimize the length of the load path in the third end portion, as the connection between the coupling member and the output member is positioned inside the annular inner part when seen along the pivot axis so that load path can extend only between the pivot axis and annular inner part. Further, maintenance and especially replacement of the actuator are facilitated, as it is merely required to withdraw the output member along the pivot axis to decouple it from the third end portion.
Here, it is particularly preferred when the base member and the output member are dimensioned such that the base member and the output member can be moved at least partially into the actuator space by a linear movement along the pivot axis and when the base member comprises at least one fixing element fixedly coupled to the base member and extending radially outwardly therefrom. The fixing element is designed such that when the first and second engagement members are in engagement with each other, the at least one fixing element abuts on an abutment surface formed on an abutment element fixedly coupled with the second end portion, the abutment surface extending transversely to the pivot axis. Such a configuration allows for a particularly simple replacement of the actuator, as it has simply to be moved out of and into the actuator space by a movement along the pivot axis. Access to the actuator is provided on that side of the bearing assembly opposite to the coupling member.
In a further preferred embodiment the first engagement member is one of a sleeve having an internal spline and a pin having an outer spline, and the second engagement member is the other of a sleeve having an internal spline and a pin having an outer spline, wherein the pin extends into the sleeve so that the internal spline meshingly engages with outer spline. Such a splined connection can be disengaged by an axial movement and allows to transmit the required torque.
Preferably, the outer spline on the pin can be formed as a curved spline such that the radial part of the outer cross section of the curved spline taken along the longitudinal axis of the pin is curved. In particular, the curved spline may be formed as a so-called crowned spline in which the root line of the spline is a radius. Further, it is also conceivable that the curved spline is a double tapered spline so that the root line of the curved spline is a shallow inverted “V”. However, other configurations of a curved spline can also be employed. The advantage of using a curved spline is that a splined coupling one member of which being a curved spline is capable to accept a certain mismatch between the pivot axis defined by the annular parts forming the bearing arrangement and the axis of the actuator. Such mismatch may be due to structure and installation tolerances.
This capability can be further improved with a configuration in which the first engagement member is formed as a sleeve having a first internal spline and the second engagement member is formed as a pin having a first outer curved spline such that the radial part of the outer cross section of the first outer curved spline taken along the longitudinal axis of the pin is curved, wherein the first outer curved spline meshingly engages with the first internal spline. Further, the base member comprises a receiving opening the internal wall of which being provided with a second internal spline, and the pin comprises a second outer curved spline which meshingly engages with the second internal spline, wherein the radial part of the outer cross section of the second outer curved spline taken along the longitudinal axis of the pin is curved. Hence, the pin is not rigidly connected to the output member of the actuator, but a splined connection with a further curved spline is employed.
In an alternative preferred embodiment at least two arm members are pivotably coupled to the output member so that each arm member may pivot relative to the output member about an axis which is parallel to the pivot axis, and each arm member is also pivotably coupled to the third end portion so that each arm member may pivot relative to the third end portion about an axis which is parallel to the pivot axis.
Here, to keep the load path as short as possible, it is particularly preferred, when the annular outer part is fixedly coupled to the second end portion of the base member and the annular inner part is fixedly coupled to the third end portion of the tip section wherein each arm member is directly pivotably coupled to the annular inner part.
For each arm member the pivotable coupling to the output member is spaced from the pivotable coupling to the third end portion when seen in a plane perpendicular to the pivot axis. In other words, for each arm member the projection of the coupling between the arm member and the output member onto a plane perpendicular to the pivot axis is spaced from the projection of the coupling between the arm member and the third end portion, so that the axes of the pivotable connections or one arm member do not coincide.
Such an arrangement is also capable to accept a mismatch or misalignment of the pivot axis defined by the bearing arrangement formed of the annular inner and outer parts on the one hand and the axis about which the base member and the output member of the actuator pivot on the other.
In order to be capable to account for a mismatch along the pivot axis it is further preferred, when each arm member is pivotably coupled to the output member by a ball member which extends into a first hole formed in the arm member and into a second hole formed in the output member.
In a further preferred embodiment the annular inner part is fixedly coupled to the third end portion whereas the annular outer part is fixedly coupled to the second end portion. The output member of the actuator comprises lug members extending radially outwards from the output member and the annular inner part comprises link members extending radially inwards wherein each of the lug members is pivotably coupled with one of the link members such that the lug member may pivot with respect to the link member about an axis that is parallel to the pivot axis. Hence, in such an arrangement the coupling assembly between the output member and the annular inner part coupled to the tip portion is in the actuator space so that the dimensions in the direction of the pivot axis of the entire coupling arrangement are kept small.
Here, it is further preferred when one of the lug members and the link members are formed such that each of the members comprises a radially extending slot open towards the other of the lug members and the link members so that each of the other of lug members and the link members extend into a slot. Further, each of the lug members is coupled to one link member by a bolt extending through aligned holes in the lug member and the link member, wherein a ball member is arranged in the hole of each of the other of the lug members and the link members, the ball member having an outer diameter corresponding to the diameter of the hole in which it is arranged and wherein each bolt extends through a through hole in the ball member. Such an arrangement also allows for a mismatch between the pivot axis defined by the annular inner and outer parts and the axis about which the output member pivots, since the connection between the lug members and the link members via a ball member is not rigid.
Finally, the above object is also achieved by an aircraft comprising a fuselage and at least one of the above-described wing arrangements.